1. Field of the Invention
This invention relates to a low cost device that is to be interconnected into a subscriber's line of any known telephone (e.g. either a rotary dial or Touch Tone telephone), whereby the telephone can be controlled by hook flash signals which are selectively initiated by the recipient of an incoming call so as to enable the recipient to return his telephone handset to the telephone cradle while temporarily placing the existing call in a hold condition.
2. Prior Art
As will be known to those skilled in the art, it is often desirable to be able to control the circuits of a telephone in the home, so that a telephone user can easily place an incoming call on hold without disconnecting the maker of the call. In this way, if the recipient is interrupted by an incoming call, he can have sufficient time to complete his task before resuming the call. Moreover, should the recipient wish to receive the call at a different or more comforable location (i.e. a telephone extension), the recipient may conveniently move to that location before resuming the call.
Several telephone control devices are available by which a user can place an incoming call on hold. By way of one example, in U.S. patent application Ser. No. 228,397, filed Jan. 26, 1981, a reliable, clip-on electronic telephone hold circuit is disclosed, whereby the recipient of an incoming call can return his handset to the telephone cradle while temporarily placing the existing call on hold so that the call can be resumed at a later time or from a different location. The hold device disclosed therein is particularly adapted to be releaseably connected to the cradle of the telephone.
Other examples of available telephone control means, which have the capability of placing the circuits of an associated telephone in a hold condition, include devices that are selectively actuated by hook flash signals generated by the telephone hook switch. More particularly, specific illlustrations of such hook flash actuated telephone control devices may be found by referring to one or more of the following U.S. patents:
U.S. Pat. No. 2,341,027--Feb. 8, 1944 PA1 U.S. Pat. No. 3,629,514--Dec. 21, 1971 PA1 U.S. Pat. No. 4,057,693--Nov. 8, 1977 PA1 U.S. Pat. No. 4,196,317--Apr. 1, 1980
However, the conventional on-hold telephone control devices are frequently characterized by one or more of the following shortcomings. More particularly, some conventional telephone control devices are typically connected directly to the telephone. Such an integral connection may prove unreliable whenever an installation, repair, or replacement of a device is required. That is, the telephone circuits may have to be modified in order to accommodate the interconnection of the control device thereto. Moreover, space consumption may be undesirably maximized, should the control device be connected at the telephone housing.
Other conventional telephone control devices are interconnected at every telephone of a multi-phone network. Hence, in order for a user to be able to receive an incoming call at a first telephone and, after placing the call on hold, to thereafter resume the call at a second or extension telephone, a telephone control device must be utilized at each telephone. Such a conventional system is both inefficient and relatively expensive to implement.
What is more, still other conventional telephone control devices include no means by which to automatically terminate a hold condition in the event that the user inadvertently and indefinitely places the telephone circuits in a hold condition. The lack of a means by which to terminate a hold condition could undesirably cause the user's telephone circuits to appear continuously busy so that the user is unable to receive additional incoming calls.
Additional conventional telephone control devices, and particularly those which are selectively actuated by means of hook switch generated hook flash signals, include no reliable means by which to distinguish between a hold command and other hook switch actuated commands, whereby a user may otherwise wish to contact the operator at the central telephone office. Accordingly, by operating the telephone hook switch in an improper sequence, a user may undesirably cause a transfer or disconnection of an existing call, instead of the placement of the call in a hold condition.